This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. CCD camera is routinely used for cryo-EM data collection. However, Quantitative tests for its performance in terms of spectral signal to noise ratio at different frequencies are needed to assess their practical limits.